1. Field of the Invention
The present invention relates to the selective chlorination of phenolic compounds with gaseous chlorine, in the ortho-position relative to the hydroxyl group.
2. Description of the Prior Art
In the preparation of chlorophenols by chlorination of phenol, isomers are produced at different stages of the reaction, ultimately giving rise to many different compounds, which must then be separated by procedures which are both expensive and difficult. Moreover, the ratios of the different isomers do not necessarily correspond to those which would be economically viable, taking into account the existing markets.
Therefore, it appeared desirable to provide selective chlorination processes, especially for selective chlorination in the ortho-position, or in the para-position, relative to the hydroxyl group of the phenolic compound.
Thus, published German patent application No. 3,318,791 describes a selective process for the chlorination of phenol into 2-chlorophenol, in a perchlorinated apolar solvent and in the presence of a branched amine.
However, the use of a solvent in an industrial chlorination process is ofttimes problematical, providing such difficulties as, for example, the need for a larger reactor volume and a more difficult separation of the reaction products.